Dr. Brante-Ramírez, Antonio

The level of parental investment for larval nutrition may determine the life cycle in marine invertebrate species laying egg masses or capsules, where the food available for enclosed individuals would determine time and developmental stage of hatching. Most species show a unique type of larval development. However, few species are poecilogonous and combine more than one development type. Poecilogony, although scarcely studied, allows comparing different patterns of parental reproductive investment, without the phylogenetic effect of the species ancestral modes of development (phylogenetic inertia), to help to understand the factors determining life strategy evolution in marine invertebrates. The poecilogonous polychaete worm Boccardia wellingtonensis encapsulates and incubates its offspring, which then hatches as either planktotrophic larvae or benthic juveniles; while Boccardia chilensis shows a non‐poecilogonous reproductive type, producing only planktotrophic larvae. In this work, we estimated the bioenergetic and biochemical composition of brooding and non‐brooding females of B. wellingtonensis and B. chilensis to compare the costs of reproduction in these two species. Results showed that glucose, protein, lipid, and energy content were significantly higher in non‐brooding than in brooding females of B. wellingtonensis; but also contained significantly more glucose, protein, and lipid than females of B. chilensis (in absolute and relative dry weight values). The poecilogonous species showed higher energy content previous to laying offspring. Our results support the idea that the evolution of a certain reproductive and life history traits in marine invertebrates is related to adaptations in the female's reproductive investment.

Poecilogony is a type of reproduction in which a species produces different types of larvae. Boccardia wellingtonensis, is a poecilogonous polychaete with females producing planktotrophic and adelphophagic larvae, in addition to nurse eggs, in the same capsule that differ in feeding behavior. It is still unclear why planktotrophs do not feed on nurse eggs during the intracapsular development and arrest its growth, while adelphophagic larvae consume nurse eggs and planktotrophic larvae inside the capsule, hatching as advance larvae or as juveniles. Here we characterized the expression of selected miRNAs from these two types of larvae and from adults in order to begin to understand the molecular mechanisms that regulate expression in this type of poecilogony. Results showed that adults and pre-hatching adelphophagic larvae have high levels of expression of miR-125, miR-87a and let-7, while adelphophages at early developmental stage had low levels of expression of miR-87b. Planktotrophic larvae showed low expression level of let-7. This work represents the first step in understanding the role of miRNAs in the development of different larval types in a poecilogonous species. We also propose to B. wellingtonensis as an interesting biological model to study the evolution of larval modes and reproductive strategies of marine invertebrates.

Of the suite of species interactions involved in biotic resistance to species invasions, predation can have complex outcomes according to the theoretical and empirical framework of community ecology. In this study, we aimed to determine the likelihood of consumptive biotic resistance within fouling communities in four ports of central Chile. Notably, we examined the influence of micro- (> 1–2 mm, < 1–2 cm) and macro- (> 1–2 cm) predators, with a particular focus on their effects on non-indigenous species (NIS). Experimental and observational approaches were combined. An exclusion experiment was carried out over 4 months to examine predator effect on the early establishment of new assemblages on settlement panels. Later successional stages upon panels were examined over a total of 26 months and supported by rapid assessment surveys in the surrounding habitats. Community structure was significantly influenced by the exclusion treatments. Macropredators reduced the fouling biomass and abundance, although conflicting patterns emerged from the exclusion of both categories of predators. Altogether, predators reduced the abundance of most NIS and cryptogenic species, some of them being only observed when the two categories of predators were excluded—a pattern generally sustained over the long-term dynamics in community development. Our results show an effective consumptive biotic resistance, furthermore possibly dependent on predator size. Further work is however needed to determine the influence of the functional diversity of natural enemies on the efficiency of biotic resistance and its interplay with other biotic interactions (competition or mutualism). A comprehensive understanding of these processes should in turn help defining management strategies in a context of habitat modification and species loss.

Homing behaviour is frequently observed in marine intertidal invertebrate species. This behaviour may help species to deal with the environmental variability of the intertidal, providing shelter during low tides and areas to explore and search for food during high tides. The capacity of individuals to show fidelity behaviour should be an adaptive trait, due to the uncertainty that finding a new shelter in each tidal cycle implies. Chiton granosus is a common polyplacophora of the Southeastern Pacific rocky intertidal zone. During high tides, individuals move throughout the substratum in search of food; meanwhile, they are found within crevices in groups of variable sizes during low tides. According to previous works, this species shows some degree of fidelity to these shelters. Using field and laboratory experiments, we herein evaluate the factors determining the degree of site fidelity in C. granosus, taking into account the distance travelled from the shelter and food availability. Also, we evaluated the importance that chemical signs from the pedal mucus have in aiding C. granosus to return to its refuge. Field observations showed that C. granosus presents variable levels of site fidelity covering a maximum distance of 50 cm from its shelter. Laboratory results suggested that fidelity to shelters is related to the proximity of food sources. Chemical cues from the pedal mucus could be used to find the shelter after exploratory activities during high tides.

In river ecosystems, spatial complexity as well as anthropogenic factors operating at different temporal and spatial scales are shaping demography, connectivity and population genetic structure of species inhabiting these habitats.Chilina dombeianais a freshwater gastropod with direct development (absence of a free larval phase) that inhabits the Biobio river basin in Chile (36 degrees S). No studies have yet evaluated the spatial patterns of the genetic diversity of this species and the potential factors that influence these patterns. Consequently, in this study, we analyzed the population genetics ofC.dombeianabased on 15 locations along the Biobio river. Eight microsatellite loci were genotyped. Also, at each sampling site, 40 environmental parameters were recorded to characterize them. Results showed thatC.dombeianahas low genetic variability with high population structure. In addition, we detected signs of historical decreases in effective population sizes, unidirectional gene flow (upstream to downstream) and contemporary demographic bottleneck. Spatial subdivisions in populations showed a pattern of isolation by distance. The redundancy analysis and variance partitioning showed that spatial components and dissolved oxygen could explain 28% of the interpopulation genetic variation, while the Random Forest analysis identified significant effects of dissolved oxygen, nitrite and total coliforms on the genetic variability of populations (22%). AlthoughC.dombeianais widely distributed in Chilean rivers, its low dispersal and specific habitat requirements make this species very sensitive to the severe increase in anthropogenic disturbances affecting river ecosystems in recent decades. Long-term monitoring of genetic population conditions and environmental parameters are needed to implement robust management and conservation policies.

Molluscan veliger larvae and some annelid larvae capture particulate food between a preoral prototrochal band of long cilia that create a current for both swimming and feeding and a postoral metatrochal band of shorter cilia that beat toward the prototroch. Larvae encountering satiating or noxious particles must somehow swim without capturing particles or else reject large numbers of captured particles. Because high rates of particle capture are inferred to depend on the beat of both ciliary bands, arrest of the metatroch could be one way to swim while reducing captures. Larvae in eight families of annelids arrest metatrochal cilia frequently during prototrochal beat, often over a large part of the metatrochal band and with the arrested cilia aligned near the beginning of the effective stroke. In contrast, metatrochs of veligers of gastropods and bivalves rarely arrested while the prototroch beat, and those arrests were more localized and variable in position. This difference in metatrochal arrest was unexpected under hypotheses of either a single origin of this feeding mechanism or multiple origins within each phylum. Although different in metatrochal arrests, larvae of both phyla can separate swimming from feeding while both prototroch and metatroch beat. One hypothesis explaining low rates of capture per encounter, without metatrochal arrest, is a change in adhesion of prototrochal cilia with algae. In a few observations, part of the velar edge was retained within the veliger's shell so that exposed prototrochal cilia contributed to swimming while the adjacent metatroch and food groove were sequestered.

Post-settlement movement has been reported mainly in marine species with low or reduced adult mobility, where distribution varies in accordance with ontogeny, thus avoiding or reducing environmental stress or biological interactions. Mussels show high dispersal at the larval stage, and settlement is a highly complex process in which larvae must choose an appropriate site to attach. Although adults are mainly sedentary, it has been shown that they move on a local scale during the benthic phase in response to physical and biological factors. Semimytilus algosus and Perumytilus purpuratus are two bioengineer mussel species cohabiting most of the Chilean rocky shores. While S. algosus occurs in the low intertidal zone, P. purpuratus dominates the mid and mid-high zones. Field and laboratory experiments have shown that S. algosus is a weak competitor with respect to P. purpuratus, and post-settlers present high mobility to relocate in the intertidal. Under this scenario, we evaluated the dispersal behavior of juveniles and adults of S. algosus as a potential response to competition with P. purpuratus. We also measured the attachment strength of S. algosus in the presence of its competitor, as a measure of its escape response ability. Our results showed that the presence of P. purpuratus increased the movement activity of juveniles and adults of S. algosus and decreased their attachment strength. Field experiments carried out with marked individuals in a Chilean rocky shore, showed that S. algosus exhibits higher local dispersion in the zone where P. purpuratus is present. Mussels' high dispersal ability throughout the whole benthic phase may not only serve to reach the optimal physiological position in the intertidal, but also to reduce competition interaction.

Growing coastal urbanization together with the intensification of maritime traffic are major processes explaining the increasing rate of biological introductions in marine environments. To investigate the link between international maritime traffic and the establishment of non-indigenous species (NIS) in coastal areas, biofouling communities in three international and three nearby local ports along 100 km of coastline in south-central Chile were compared using settlement panels and rapid assessment surveys. A larger number of NIS was observed in international ports, as expected in these ‘invasion hubs’. However, despite a few environmental differences between international and local ports, the two port categories did not display significant differences regarding NIS establishment and contribution to community structure over the studied period (1.5 years). In international ports, the free space could be a limiting factor for NIS establishment. The results also suggest that local ports should be considered in NIS surveillance programs in Chile.

The mussels Perumytilus purpuratus and Semimytilus algosus are two dominant species of intertidal rocky shores of central Chile. These species have marked differences in their distribution patterns with P. purpuratus dominating the mid-intertidal zone and S. algosus dominating the lower intertidal zone usually in habitats influenced by sand. Although it has been suggested that differences in tolerance to environmental conditions, such as air exposure and presence of sand, can explain the distribution of these species, there are currently no experimental studies to support such hypotheses. Here, we evaluated the growth and survival rate in the field of both mussel species at four different tidal heights: 25, 75, 135, and 175 cm above the zero tide. In addition, filtration rates were estimated for both species in the presence and absence of sand in laboratory conditions. The results showed that shell and wet weight growth rates of P. purpuratus were highest in mid- and medium-high tidal heights, whereas the growth rate of S. algosus was highest in the medium-low level. Similar pattern was observed for survival percentage. Furthermore, small S. algosus individuals cultivated with sand in suspension had significantly higher filtration rates than P. purpuratus. In large individuals, no differences were observed between the two species nor between treatments (presence and absence of sand). These results indicate that the differences in the distribution patterns of P. purpuratus and S. algosus in the intertidal can be explained by differences in physiological tolerances to both air exposure and to the presence of sand.

One of the most important issues in biological invasions is understanding the factors and mechanisms determining the invasion success of non-native species. Theoretical and empirical works have shown that genetic diversity is a determinant of invasion success; thus, studying spatial patterns of genetic diversity, and exploring how biological and physical factors shape this population trait, are fundamental for understanding this phenomenon. Coastal marine ecosystems are one of the most susceptible habitats to invasion given the complex network of maritime transport. In this work we study the cryptogenic anemone, Anemonia alicemartinae, which has rapidly increased its geographical range southward during the last 50 years (approx. 2000 km) along the southeastern Pacific coast. Based on COI mtDNA sequences we evaluated three main hypotheses: a) the genetic diversity of A. alicemartinae decreases according to the direction of invasion (from north to south); b) there is biogeographic–phylogeographic concordance at the 30°S biogeographic break; and c) the demographic history is coherent with a recent geographic expansion. A total of 161 individual samples of A. alicemartinae were collected along the southeastern Pacific coast range of distribution, covering more than 2000 km, including samples along the 30°S biogeographical break. Results showed low genetic diversity (Hd = 0.253; π = 0.08) and a lack of geographic population genetic structure (FST = − 0.009, p-value = 0.656). The highest genetic diversity was observed in Peru (Chero and Mesas) and at localities close to the main Chilean seaports. We did not observe concordance between biogeographic and phylogeographic patterns or isolation by distance. Demographic indices (D = − 2.604, p < 0.001; Fu's = − 26.619, p < 0.001), as well as a star-like configuration of the haplotype network support recent population expansion of this species. Our results, together with historical field observations, support the idea that the current distribution of A. alicemartinae may be explained by an increase in population size from one small ancestral population probably from the south of Peru, with subsequent human-mediated southward transport, probably associated with regional-scale maritime activities.